KR20010020139A - A fuel injection pump for internal combustion engines, in particular big, slow marine diesel engines - Google Patents

Abstract

A fuel injection pump for supplying a variable amount of fuel to the injection nozzles disposed in the working cylinder of the engine, the injection nozzle is provided with a needle having a spring built in the nozzle hole, the injection pump is a barrel (2) And a plunger (3) having a top edge (4) formed between the side and the end face and at least one spirally extending inclined transition edge (6) in the barrel, the inclined The turning edge forms a groove 5 on the side of the plunger, the groove communicating with the end face of the plunger through an axial passage, the wall of the barrel having at least one switching hole 11, the hole being Open to the circumferential supply chamber for receiving fuel under moderate pressure, the hole being blocked by the side of the plunger below the top edge during movement from the bottom position of the plunger to the upper position and then effective The orifice member is at least at the end of the stroke stroke so that it is not blocked by the inclined diverting edge for diverting excess fuel, and the orifice member is at least reduced so that the aperture is reduced relative to the cross section of the hole to provide increased static pressure at the diverting hole during a portion of the plunger movement. A fuel injection pump for an internal combustion engine, in particular a large low speed marine diesel engine, provided in some holes. In order to overcome the problems caused by erosion and pressure oscillations in large pumps, the pump comprises flow restricting means 13 with at least one switching hole 11 arranged away from the wall of the barrel, which means and the barrel A chamber 20 is formed between the cylindrical walls of (2).

Description

FUEL INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES, IN PARTICULAR BIG, SLOW MARINE DIESEL ENGINES}

In a typical fuel injection pump, each inclined transition edge is matched with a hole through the wall of the barrel, the plunger such that the hole is blocked by the upper edge of the plunger at the beginning of the movement of the plunger, and the set fuel is injected When supplied to the nozzles the hole is also exposed by the inclined turning edges thereafter. Such an arrangement will work satisfactorily in small and medium sized engines, but in large, low speed diesel engines the size and dimensions of the pump should be taken to dampen pressure variations in the injector at the beginning and end of the effective pump stroke. Problems arise. Such problems can be due to erosion at the sides of the plunger which prevents cavitation in the holes due to the high flow rate. However, an increase in the cross section of the holes cannot be achieved soon, because the holes must be delayed by exerting a constant flow resistance if they are not blocked by the inclined turning edges. This delay is necessary to prevent the combustion gas from entering the injection nozzle and to prevent cavitation at the nozzles. In addition, when a fuel having internal lubrication properties is used, it is desirable to obtain a substantially large bearing surface between the plunger and the barrel in order to reduce the risk of fusion in the region of the upper edge of the plunger.

The prior art of the type described above is described as less effective in US-A-5 015 160, which sets a pressure of 50 bar in the annular space around the barrel while closing the pressure relief hole. A device is disclosed. The pressure is maintained by the non-return valve of the suction pipe and the pressure valve with the spring of the return passage.

The present invention relates to a fuel injection pump for an internal combustion engine, in particular a large low speed marine diesel engine, the injection pump supplying a variable amount of fuel to an injection nozzle disposed in an operating cylinder of an engine, the injection nozzle being connected to a nozzle hole. A spring-loaded needle is provided, wherein the injection pump comprises a barrel, the barrel having a plunger having a top edge formed between side and end faces and at least one spirally extending inclined transition edge. Moveable inwardly, the inclined diverting edge forming a groove in the side of the plunger, the groove communicating with an end face of the plunger through an axial passageway, the wall of the barrel having at least one transition hole The hole is opened to a circumferential supply chamber for receiving fuel under a suitable pressure, the holes being positioned upwards from the bottom position of the plunger. During movement it is blocked by the side surface of the plunger below the upper edge portion in to, and is not at the end of the effective pump stroke is not blocked by the switching sloping edge portion for the conversion of the excess fuel.

1 is an axial sectional view of a fuel injection pump according to the invention;

2 is a partial cross-sectional view of the barrel wall by line II-II according to FIG. 1.

3 is a diagram showing the pressure of a fuel injection pump according to the invention during fuel injection.

4A, 4B and 4C schematically show blocking holes in the longitudinal section.

It is an object of the present invention to provide a fuel injection pump with simple yet reliable means for effectively preventing erosion in the region adjacent the upper edge of the plunger.

This object is achieved according to the invention by the features of the fuel injection pump described in the characterizing part of claim 1.

In the fuel injection pump according to the invention, means for restricting the flow are arranged in the switching holes formed in the wall of the barrel. Thereby, a significantly increased pressure is created in the space between the flow restricting means and the plunger, the flow restricting means being merely an orifice member, the pressure being at the upper edge of the plunger irrespective of the instantaneously generated high flow pressure. It effectively prevents the occurrence of cavitation in adjacent areas. Although the increased pressure by the orifice member is relieved, significant flow rates occur and the means have been shown to be extremely simple compared to the prior art and effective in preventing plunger erosion by transferring pressure to other areas or preventing cavitation from occurring. .

The present invention relates to a fuel injection pump in which the start and end of an effective pump stroke are controlled by a plurality of sets of holes. According to the invention, the orifice member is arranged in the holes starting the pump stroke.

According to the invention, the orifice member has a hole such that the static pressure in the upper forward switching hole reaches 10-20% of the delivery pressure of the pump. Large decelerations on the delivered fuel have not been shown to have an undesirable effect on pressure build-up prior to fuel injection.

The invention is explained in more detail with reference to the accompanying drawings.

In the axial view of FIG. 1, the fuel injection pump 1 comprises a barrel barrel 2 in which the plunger 3 is movable. The barrel 2 consists of a pump housing of a conventional type, comprising a supply chamber surrounding the middle of the barrel, allowing excess fuel to be delivered therein, from which fuel is supplied to the barrel during the return stroke of the plunger. It is done. The plunger 3 comprises a top edge 4 formed between its end face and side surface. The plunger further comprises a groove 5 formed by an inclined turning edge 6 extending helically along the side of the plunger in the direction of its end face. The inclined, transitional edge 6 is for example formed at an angle of 120 ° and the plunger is typically provided with two transitional edges 6 arranged opposite one another. The barrel 2 is provided with a connecting means 7 for the rotating mechanism, whereby the plunger can be rotated for adjusting the delivery flow rate, and the connecting means 8 is a roller guide for moving the plunger in the axial direction. . The rotating mechanisms are not the object of the present invention and are those commonly used. The plunger 3 also includes an axial passage 9 which communicates the groove 5 with the space 10 above the end face of the plunger.

The injection pump is adapted to deliver variable capacity fuel to the injection nozzles of the working cylinders of the diesel engine. The amount of fuel delivered thereby is adjusted by the rotation of the plunger 3. When the effective pump stroke begins, the plunger blocks the timing holes and the transition holes 11 formed at the corners of the end face 4 in the barrel 2 of the injection pump during its upward movement, and then the effective pump stroke is terminated. When the inclined turning edge 6 does not block the pressure relief holes 12, the axial passage 9, the groove 5, and the switching hole 12 to the supply chamber around the barrel barrel 2. Fuel is discharged to relieve pressure in the pump chamber above the end face 4 of the plunger.

For example, in fuel injection pumps for large, low speed diesel engines for ships, special problems arise due to the large size of the pump and the high pressure at which the fuel is injected, which problems affect the beginning and end of the effective pump stroke. This is solved by the above-described injection pump using the specially designed timing holes and pressure relief holes. The timing holes are formed to effectively prevent cavitation that hinders fuel flow being discharged at high speed. In addition, the pressure relief holes are configured to obtain adequate damping of the inverted fuel or to prevent cavitation in the injection nozzle until the risk of pressure vibration, which may cause gasoline in the cylinder to enter the injection nozzles, is eliminated. Moreover, the bearing surface between the top of the plunger and the wall of the barrel can be configured to a suitable size by making the axial spacing between the holes 11 and 12 the appropriate dimensions.

The timing holes have a larger cross section than the pressure relief holes 12. Cavitation is however most effectively prevented by disposing the orifice member 13 at the timing hole outlet to the supply chamber as shown in FIG. The flow passage by the orifice member is configured such that the pressure in the timing hole in front of the orifice member exceeds the pressure in the supply chamber just before the switching hole is blocked when the corner portion of the end face 4 of the plunger passes. .

The pressure relief holes 12 which are not blocked by the inclined turning edge 6 have a diffuser shaped longitudinal contour and are configured to have the smallest cross section in the wall of the barrel. It is necessary for the pressure relief holes to have a small cross section in the wall of the barrel as above to obtain a sharp exposure of the hole and to obtain a precise pressure change in the injector.

The diagram in FIG. 3 shows the pressure change in the fuel injection pump according to the invention derived as a function of crank angle. The fully drawn curve shows the pressure of the pump chamber 10. The curve shows the pressure of the pump chamber that begins to increase as soon as the plunger 3 is moved upwards, where the timing hole 11 is blocked by the plunger below its upper edge 4 and is set in the subsequent pump stroke. Fuel is injected into the engine's working cylinder. At the point 16, the switching holes are not blocked and the pressure in the pump chamber falls in the damping process and counteracts the pressure oscillations in the injector, so that the needles perform the correct closing action on the injection furnaces. Dotted line 17 shows the pressure change in the chamber between the side of the plunger and the orifice member, the chamber being provided with an orifice member 13 of appropriate size. It is shown that a gradual pressure drop can be obtained, which effectively prevents cavitation in the side holes adjacent to the plunger side.

The invention is not limited to fuel injection pumps in which timing and switching holes are formed separately in the pump barrel, but can be used successfully in fuel injection pumps, where the number of switching holes is equal to the number of inclined switching edges of the plunger. In other words, the start and end of fuel injection are made by the same holes formed in the wall of the barrel. In such a pump, the flow restricting means consists of means for preventing cavitation and for preventing erosion of the plunger associated therewith, which means controlling the drop in pressure during pressure relief at the end of the effective pump stroke.

4A, 4B and 4C show longitudinal cross sections of switching holes of schematic embodiments. FIG. 4A shows an embodiment in which the flow restricting means in the form of an orifice member 21 is arranged in the switching hole 20 in proximity to the outlet 22 to the supply chamber. In this embodiment, the chamber of maximum size is pressurized by the switching holes and the pressure is relieved, as a result of which the maximum possible volume of the chamber and the maximum possible pressure retention of the chamber between the orifice member and the inlet are achieved. The orifice member may consist of a plurality of passages or in the flow direction of the passages at an angle with respect to the axis of the switching hole. The advantage of the passages angular with the axis of the diversion hole is that the pressure relief fluid does not come into vertical contact with the opposite feed chamber wall, reducing the risk of erosion of the feed chamber wall. The chamber between the wall of the barrel and the orifice member may further be non-cylindrical. This shape can be, for example, conical in that the switching holes formed in the wall of the barrel are somewhat smaller than the diameter of the supply chamber, into which the orifice member is inserted. In this way the flow control effect acts on the holes and orifice members formed in the wall of the barrel, which can be beneficial in the absence of separate timing and switching holes.

In FIG. 4B, the orifice member 23 is arranged close to the middle of the hole 20 so that the chamber can be made smaller and the distance between the orifice member 23 and the opposite wall of the supply chamber can be made larger. Wherein the fluid flowing from the orifice member can cause erosion.

4C shows preferred embodiments of the changeover hole 20 provided with an orifice member. The orifice member 24 is arranged in the middle of the switching hole so that the switching hole is formed as the diffuser 25 in the direction toward the outlet 22 to the supply chamber. The purpose of the diffuser 25 is to reduce the jet blowing speed leaving the orifice member. Due to the proper dimensions of the orifice members 21, 22 or 24, the pressure rises in front of the orifice member of the changeover hole when the changeover hole is blocked, eliminating the risk of cavitation, and the pressure relief damping reduces the pressure without significant pressure vibration. Degradation can also be made. If necessary, additional damping can be achieved by proper design of the axial passages of the plunger.

Claims (3)

A fuel injection pump for supplying a variable amount of fuel to the injection nozzles disposed in the working cylinder of the engine, the injection nozzle has a needle with a spring built in the nozzle hole, the injection pump includes a barrel A plunger having a top corner formed between the side and the end face and at least one helically extending inclined transition edge is movable in the barrel, the inclined transition corner forming a groove in the side of the plunger, The groove communicates with the end face of the plunger through an axial passage, the wall of the barrel has at least one switching hole, the hole is opened to a circumferential supply chamber for receiving fuel under moderate pressure, and the hole is During movement from the bottom position of the plunger to the upper position, it is blocked by the side of the plunger below the upper edge and then the end of the effective pump stroke The orifice member is not blocked by the inclined diverting edge for diverting excess fuel, and the orifice member is reduced to at least some of the holes so that the orifice is reduced relative to the cross section of the hole to provide increased static pressure in the diverting hole during a portion of the plunger movement. In a fuel injection pump provided for an internal combustion engine, in particular a large low speed marine diesel engine, the means for increasing the static pressure is an orifice member accommodated in the changeover hole, and a pressure rise occurs in the changeover hole at the front side of the orifice member before and after the changeover. And a reduced cross section with respect to a cross section of the switching hole. The fuel injection pump according to claim 1, wherein the start and end of the effective pump stroke are controlled by separate holes and the orifice member is disposed in the holes for starting the pump stroke. 3. The fuel injection pump according to claim 2, wherein the orifice member has a hole such that the static pressure in the upper front switching hole reaches 10-20% of the pump delivery pressure.